For example, semiconductor light emitting devices using nitride semiconductors of gallium nitride (GaN) and the like have been applied to ultraviolet, violet, blue, and green light emitting diodes (LEDs), bluish-violet and blue laser diodes (LDs), and the like.
In a semiconductor light emitting device, it is desirable to improve the crystallinity and increase the luminous efficiency.
In an LED, for example, although a semiconductor thin film structure made of GaN is stacked mainly on a sapphire substrate, the light produced by the semiconductor layer tends to be trapped easily in the GaN semiconductor layer because the refractive index differs greatly between the GaN semiconductor and the sapphire. Conversely, there is a method in which an unevenness is provided in the surface of the sapphire substrate to increase the light extraction efficiency. However, even when such a structure is used, there is room for improvement to increase the efficiency.